This contract modification is to extend and supplement Contract HHSN271201000033C, consistent with the scope of work of Study of Health Outcomes in Children with Autism and Their Families in order to access the currently validated database developed under the contract to provide for further analysis . Autism Spectrum Disorder (ASD) is a significant public health concern, with an estimated prevalence of 1 in 88 children in the United States. Much of the research to date has focused on the core social and communication deficits of ASD, but there are anecdotes and some survey data suggesting that the rate of comorbid health conditions may also be elevated in this population. Furthermore, despite several large-scale epidemiological studies that have assessed but not found any potential association between ASD and vaccinations, public concerns persist about such a causal link. At least partly as a consequence, health officials in the United States have reported an increased rate of vaccine refusal in the general population. The Study of Health Outcomes in Children with Autism and their Families was begun two years ago. Under this contract, the Contractor analyzed a large dataset of retrospective commercial health plan claims of 46,236 children with ASD, their parents and siblings, and a comparison cohort of children and family members. They successfully completed the analyses requested in the original statement of work, which included a study of the validity of ASD diagnoses in the claims data, and descriptions of health outcomes and health care utilization of the ASD cohort, their family members, and the comparison cohorts.